WHAT a joke. The trial of allegedly stumbling-drunk Judge Donna Mills took a turn from the ridiculous to the uproarious yesterday, as members of the jury caught a serious case of the giggles.

During an afternoon lull, two female jurors started snickering. Then a man joined in. Then another lady. Pretty soon, five jurors were guffawing so loud they almost drowned out the lawyers.

What’s so funny? Where’s the humor in a Manhattan Supreme Court justice who downs a river of Scotch, drives her daddy’s Rolls Royce to Loehmann’s and bumps into two parked cars?

Find me the laughs in the case of a woman – a judge – who refused a Breathalyzer test, allegedly kicked a cop, then screamed that she’s the victim of racial profiling?

Because Mills’ offensive defense rested yesterday after calling a single witness – a Rolls mechanic who said the car tended to “lurch” – I guess Mills’ confident swagger is based on a pretty good hunch.

This jury just might be buying what she’s selling.

Defense lawyer Paul Gentile yesterday asked a cop why Mills – described by witnesses as soused, belligerent, stumbling and slurring on the night of July 22, 2002 – had to be handcuffed behind her back.